Fuel storage tanks on vehicles usually serve for storing fuels that are delivered to engines that power vehicles. For example, airplanes are usually driven or propelled by kerosene which is stored in wing and mid-section tanks. It is increasingly desirable and necessary to use alternative forms of energy. The increasing awareness of the environmental impact of engine exhaust on sensitive regions of the atmosphere by aircraft engines, and, in connection therewith, the strengthened regulations for limiting emissions of pollutants, require a search for alternative fuels. Also, the availability of fossil fuels produced from oil is limited and exhaustible. Therefore, it is essential to develop alternative fuels, such as cryogenic fuels. Cryogenic fuels are gaseous at room temperature, but become liquid at very low temperatures and/or high pressures. Liquified hydrogen and liquified natural gas have proven particularly suitable. Since the use of hydrogen is particularly friendly to the environment and may be generated from water, for example, by means of solar energy or wind energy, hydrogen is a focus for development by the aviation industry.
For receiving and storing cryogenic fuels, special safety provisions are required. Hydrogen, especially in the gaseous state, shows a high reactivity with respect to oxygen and other oxidizers. This means, that contact of hydrogen with oxygen contained in the air may lead to an unwanted reaction in the form of a deflagration, ignition, explosion or the like. Known storage tanks are insufficient to safely separate hydrogen from its surrounding with the necessary reliability. Furthermore, known fuel tanks are usually not fire-proof and provide insufficient protections against ignition of fuel. Particularly in the case of hydrogen, there exists the danger that fuel in the surrounding hydrogen tanks will be ignited causing a fire to spread in an uncontrolled way. Thus, known fuel storage tanks present an unacceptable safety vulnerability, particularly when disposed in an operating airplane.
It would be desirable to have a cryogenic storage reservoir for fuels such as hydrogen that prevents contact with oxygen and inhibits the spread of fire.